Telecom equipment requires power to operate, and in the field where possibilities of providing local power supply are scarce, telecom copper cable can be utilized to transport a large amount of power from a remote supply whereas power transport capabilities of optical fibre are very limited. With the advent of deep fibre broadband access networks and small-cell mobile networks requiring broadband backhaul, i.e. architectures for providing fibre deeper in the access network and eventually all the way home to the subscribers or base-station location, some network architectures require data and telecommunication nodes to move from a central office into the field to achieve an increase in bandwidth over the user/backhaul drop. Such field nodes are typically fed by fibre without capability to transport power.
Typical architectures are fibre-to-the-cabinet networks, i.e. fibre is drawn to a street cabinet that is located within about 300 m from the user's premises where the transport media from the cabinet to the user is copper cable, and small-cell site nodes such as e.g. macro, micro and pico cells. These new architecture require new approaches to power the field nodes as direct access to the power grid is not available in remote locations or the remote power transfer from the operator's point of presence is very costly and energy-inefficient.
In the days of POTS, the telecom node was located at a central office and the associated telecom equipment provided power to a network terminal at a customer premises via twisted-pair copper cable and no local power supply was needed at the customer. Today, at least over shorter distances—IEEE 802.3af (“Power over Ethernet”) and IEEE 802.3at (“Power over Ethernet+”) allow to transport several tens of Watts over CAT cables in addition to data transport. In both scenarios, operators provide and pay the power. However, power loss in the copper cable is major.
In typical xDSL and fiber-to-the-home deployments, the equipment of the telecom node is powered at the central office and the network terminals at the user.
Now, in case the network node is moved from the central office to a field location, which is done in fiber-to-the-cabinet deployments as well as next-generation radio networks, the network node being for example and passive optical network (PON)-fed IPDSLAM (IP DSL Access Multiplexer) or a radio base station, the network node is powered either directly from the central office (which is ineffective) or by a remote power unit located in the field utilizing existing (long-reach) copper infrastructure once used for lower-rate xDSL technologies. As in the case of centralized powering, responsibilities for providing/maintaining power are clear—the operator answers for the central office and network node equipment while the user pays for the powering of the network terminal. Remote power feeding architectures have proven to be technically complex/expensive, energy-inefficient, and strictly regulated in terms of safety. For instance, power may have to be transported over long distances thus requiring high voltages at up to 380V@300 mA.
A further approach for field-located network nodes is reverse powering; the equipment of the field telecom node is powered reversely from the local mains of individual customer homes utilizing existing copper used for data transmission from the field node to the customer premises equipment. Hence, the filed node is powered by the users that it is servicing and the power loss is relatively low as the distance from the filed node to the user premises typically is short. With this approach, several users typically power the network node. Reverse power feeding is technically less complex than remote powering, but has been critically perceived by network operators due to legal issues and contractual problems—net contribution of each individual user to the total amount of power provided to the telecom node for servicing the users is not clear.